The invention relates generally to flywheels and, more specifically, to a soft start, high inertia flywheel for use with tub grinders.
Flywheels have been used for many years dating back to the steam engine and single cylinder gas engines to produce inertia to carry the load between piston firings. Many mechanical systems use flywheels to stabilize the rotation of the engine and the driven equipment.
A tub grinder has a tub-shaped enclosure including a circular floor, generally cylindrical sidewalls and an open top. An example of a tub grinder is described in U.S. Pat. No. 5,950,942. Material to be comminuted by the tub grinder is added to the tub through the open top. A hammermill rotates at a high speed along a typically horizontal axis below the floor of the tub. The outer periphery of the hammermill extends above the floor of the tub to come into contact with the material to be ground. Most tub grinders are mounted on vehicles for transport to sites of material to be ground.
Tub grinders are used to grind a wide variety of materials including stumps and logs. Gravity is essentially used to feed the material to the hammermill that makes the flow and quantity of material entering the hammermill very inconsistent and uncontrolled. As a result, the rpms of the drive engine of the hammermill frequently go up and down, sometimes even jamming the hammer milt and stalling the engine. A large flywheel would stabilize the engine rpm's and help prevent jams when the hammermill attempts to grind too much material.
If a flywheel is to be attached to the hammer mill, it must be located outside the tub diameter. Preferably, the flywheel is located just outside the tub diameter but still mounted directly to the hammermill so as to most effectively transmit its inertia load into the grinding process.
There are five problems with flywheels on hammermillson mobile equipment; weight, bearing support, torque limiting, and startup and slowdown control.